1. FIELD OF THE INVENTION
The invention relates to improvement in fuel flow meters of the type having a vertically upwardly extending sight glass for directly visually indicating the flow rate of fuel therethrough. More particularly, the invention relates to a fuel flow meter of the foregoing type having means reducing the accumulation of vapors in the sight glass and reducing turbulence adjacent the metering orifice to obtain more accurate flow rate indications.
2. DESCRIPTION OF THE PRIOR ART
Various prior constructions of fuel flow meters of the type having an upwardly extending sight glass portion through which fuel flow rates may be visually observed or indicated have included a vertically slidable rod, the upper end of which is received in the sight glass portion to provide the visual indications and the lower end of which is provided with a disc or float-like member such as shown in U.S. Pat. Nos. 1,215,129, 1,989,366, 2,073,372, 2,076,562, 2,293,987, 2,388,672, 2,955,465 and 2,350,343. The disc or float member is freely vertically slidable in a particularly shaped metering chamber and may extend through an upper or lower orifice or restriction in the vertical flow meter. Various problems and undesirable operating characteristics have been encountered with such meter constructions, which are set forth in and which are largely eliminated by my fuel flow meter construction of U.S. Pat. No. 3,117,446.
Several minor problems and difficulties have been encountered with the fuel flow meter construction of the type shown in my patent, as well as being present in other meter constructions set forth in the patents listed above. Fuel vapors will collect in the sight glass, especially during stop and go driving in warm weather, which seriously affects the damping action between the pin head and sight glass in thos constructions where the pin head is used to achieve a damping action. These fuel vapors or bubbles in the sight glass affect the accuracy of the metering being provided. Another problem encounterred with such prior meter constructions is the exact manufacturing tolerances required in the sight glass tube or chamber and needle head where the metering needle head is used as the damping means in combination with the sight glass. Such precisioned manufactured and machined parts increase considerably the cost of the fuel flow meter since most of the commercially available low-cost glass or plastic tubing used for the sight glass is not provided with the required internal bore linearity and uniformity.
Still another minor problem encountered with meter constructions of the type shown in my U.S. Pat. No. 3,117,446, is the creation of turbulence in the area of the metering orifice. The fuel or liquid being measured flows upwardly through the restricted orifice at a relatively high rate of speed, which flow then must reverse and flow downwardly through the outlet holes located just above the metering orifice inside the tubular body which creates turbulence with the incoming upwardly flowing fuel. A further shortcoming of such prior meter constructions is the formation of the metering orifice at a central position in the interior bore of a tubular member requiring machining from both the upper and lower ends of the tube to form the orifice, which tube also must be provided with external threaded areas for attaching and mounting additional components thereon. Again, this precision machining at a relatively difficult location on the tubular member to form the orifice increases the cost per unit of prior meter constructions. Still another shortcoming of such prior meter constructions is the inability to use such constructions to measure the fuel flow rate of fluids other than the particular fluid (gasoline) for which it was designed, since the density of the fluid being measured affects the reading due to the buoyancy exerted on the specifically weighted and designed metering needle, disc or float member mounted thereon.